Receiver Diversity in LEO Satcom Constellations

Low-earth orbit (LEO) satellites can enable connectivity for simple, low-power user terminals and have been a significant point of research for upcoming 6G applications. These devices, however, often lack high-power amplifiers and high-gain antennas. Coupling these factors with multipath and shadow fading as well as significant path loss, the achievable signal-to-noise ratio (SNR) at the satellite can be very low in these systems. However, in dense LEO constellations, it is not uncommon for multiple satellites to be in view of a user terminal. By employing joint reception over multiple satellites and an intelligent combining scheme, the received SNR can be substantially improved. Furthermore, time diversity due to the motion of the satellites relative to the user terminal can improve the probability of message reception. In this paper, we quantify the potential performance improvements of different combining approaches, including the effects of different crosslink configurations which may limit the capabilities of combining schemes.